Making a color coding with nixie tubes is tedious because it needs a lot of combinators.
So..
Why not setting the nixie's color based on the signal value and thresholds passed on color signals?
Set a tube with "use colors" and listen to signal A. Pass it red=10, green=20, and make the display color be default-orange if A<10, red between 11 and 20, green above
(note: I started my own fork of your code, but I'm currently struggling with cache)
